AND LIFE-HISTORY OF A TROPICAL EPIPHYLLOUS LICHEN. 97 
pedicel from the inner two thirds. It must be borne in mind that some protoplasm, as well 
as starch and orange-red drops remain in all these parts, although by far the larger portion 
has now been passed on to the ovoid zoosporangium at the end of each pedicel. It so 
happens that a curious mechanical action is brought about by the above disposition of the 
parts. When the uninjured fertile hair and tuft are moist and turgid, the pedicels all 
radiate stiffly from the central cell, and support the ovoid zoosporangia obliquely attached 
to their ends in such a manner that one end of the egg, so to speak, faces directly 
downwards, towards the plane of the thallus beneath; when, on the contrary, the parts 
are drier and consequently less turgid, the pedicels contract and fold, each on itself, and 
draw the zoosporangia closely around the central or head cell, into a sort of compact 
nest. The septum which separates the pedicel from the zoosporangium is not a simple 
complete wall of cellulose across the whole diameter, but remains open in the centre for 
some time. The junction of the two bodies, just before the latter falls, is of a peculiar 
nature; and on the detached ovoid body are seen two concentric circles (fig. 33), corre- 
sponding, apparently, to two areas of attachment, as follows. 
When the septum first forms between the pedicel and the ovoid body, it only constricts 
the originally wide aperture by about one half, a circular hole still remaining in the centre 
and affording communication between the contents of both pedicel and zoosporangium. 
When the zoosporangium is ripe this little hole becomes covered by a lamella of cellulose, 
which is so far a new structure that it appears patched, as it were, on to the older partial 
septum. The consequence is, that just before maturity the two structures are united by 
two concentric areas of attachment—an outer old one, and an inner newer опе”, In this 
way only can I explain the constant appearances figured at Pl. XX. figs. 29, 32 & 33; 
compare figs. 30 & 31. 
It has been already stated that finely granular protoplasm and food-materials, in large 
quantities, become passed on into the ovoid young zoosporangia through the pedicels &e. 
After becoming clearer and still more finely divided, the now bright orange-coloured 
contents slowly accumulate at many centres, and form numerous densely packed spherical 
bodies (figs. 29-31). 
Meanwhile at that pole of the zoosporangium which faces downwards a papilla arises, 
apparently from the softening and thinning of the cellulose wall; this absorbs water, and 
soon comes to look like a pale drop projecting from the surface. I have no conclusive 
proof that any of the protoplasmic contents participate in the formation of this diffluent 
droplet; nevertheless in some cases (fig. 81 а) the contents appear to be pushing the 
papilla outwards, while some hours afterwards (in water) they may contract away from © 
it (6 & c), even after the hyaline papilla has opened. Some time after this the small 
spheres, having become isolated from one another, commence to make their way out by a 
circular hole corresponding to the point where the drop-like swelling described above 
was formed, each becoming a distinct motile zoospore (figs. 85 & 36). 
Each zoospore, when fully formed, is so like the spherical later state of the similar 
bodies emitted from the cells embedded in the thallus, that it becomes very difficult to 
* An equally curious and more complex phenomenon of a similar kind occurs in Ballia callitricha, according to 
Archer (Trans. Linn. Soc. 2nd ser. Bot. i. p. 212). 
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